Wiring board and method of producing the same

ABSTRACT

A wiring board includes: wiring layers; insulating layers disposed between the wiring layers; and external connection pads respectively including surface plated layers, for connecting to an external circuit. In each of the external connection pads in one face of the wiring board, an outer peripheral edge of the external connection pad is retracted from an outer peripheral edge of the surface plated layer toward a center of the external connection pad.

This application claims priority from Japanese Patent Application No. 2008-305154, filed on Nov. 28, 2008, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a wiring board and a method of producing the same, and more particularly to a wiring board of a type in which pads for mounting a semiconductor chip or the like are disposed on one face, and pads for connecting with another mounting board are disposed on the other face.

DESCRIPTION OF RELATED ART

In a wiring board which is used, for example, in packaging of electronic components such as a semiconductor chip, pads for mounting a semiconductor chip, an electronic component, or the like are disposed on one face, and pads for connecting with another mounting board are disposed on the other face. In order to attain joining with solder bumps which are used for connections with a semiconductor chip or the like, and those with a mounting board, a surface plated layer is formed on each surface of such external connection pads. A surface plated layer is formed by thinly plating nickel (Ni), gold (Au), and the like from the side of the pad.

FIG. 27 shows an example of an external connection pad in a wiring board which is produced by a usual build-up technique. The external connection pad 101 is formed on the outermost insulating layer 102 of the wiring board, by a conductor material such as copper (Cu), and, at a position corresponding to the external connection pad 101, connected through a via 105 which is passed through an insulating layer 102, to a pad 104 which is formed in one end of a lower wiring 103. A solder resist layer 106 is disposed on the outermost surface of the board, and an opening portion 107 through which a part of the upper face of the external connection pad 101 is exposed is formed in the solder resist layer 106. A surface plated layer 108 is placed on the exposed upper face of the external connection pad 101.

As a method of producing a wiring board, Domestic Re-publication of PCT Patent Application No. 2003/039219 discloses in which a core board for alternately forming a wiring layer and an insulating layer on both the front and rear faces of the wiring board by a build-up technique is not used, external connection pads are first formed together with surface plated layers on a support member such as a copper plate, a required number of wiring layers and insulating layers are formed on the external connection pads by a build-up technique, external connection pads are formed on the opposite side, and thereafter the support member is removed, thereby forming a wiring board.

FIG. 28 shows an example of an external connection pad (that is initially formed on the support member) on one face of the wiring board which is produced by the method. In the external connection pad 121, one side is covered by a surface plated layer 122, and the surface of the surface plated layer is exposed from that of the outermost insulating layer 123. The external connection pad 121 is connected through a via 124 which is passed through the insulating layer 123, to a pad 126 which is formed in one end of a lower wiring 125. An external connection pad on the other face of the board is configured in the same as that which has been described with reference to FIG. 27.

In the external connection pad 101 of FIG. 27, the opening portion 107 is formed in the solder resist layer 106 that is formed so as to cover the whole face of the board after the formation of the pad, and a part of the pad is exposed for connection with a semiconductor chip or an external circuit. Therefore, the pad 101 must be formed larger than the opening portion 107 of the solder resist layer. This configuration hinders miniaturization of wirings.

Since the external connection pad 101 is formed in a large size, the amount of a resin which is between the pad 101 and the pad 104 of the lower wiring (specifically, the resin which is surrounded by vertical broken lines A shown in FIG. 27, the lower face of the pad 101, the upper face of the pad 104, and the side face of the via 105) is large, and hence there is a possibility that the connection reliability of the via is lowered by, for example, formation of a crack in a connecting portion between the pads and the via and due to stress caused by heat shrinkage of the resin.

In the case of the external connection pad 121 of FIG. 28, it is possible to solve the above-discussed problems. However, the surface plated layer 122 and the pad 121 therebelow have the same size, and hence a crack 131 which is formed due to stress between the surface plated layer 122 and the insulating layer 123 easily propagates toward the interior of the insulating layer 123 along the side face of the pad 121, thereby producing breakage of the wiring or the like. Therefore, this disadvantage tends to cause the performance of the wiring board to be degraded.

SUMMARY OF INVENTION

Illustrative aspects of the present invention provide a wiring board and a method of producing the same in which external connection pads that do not hinder miniaturization of wirings, that can maintain the connection reliability of vias, and that hardly cause degradation of the performance of the wiring board are formed in one face of the wiring board.

According to a first aspect of the present invention, a wiring board includes: wiring layers; insulating layers disposed between the wiring layers; and external connection pads respectively including surface plated layers, for connecting to an external circuit. In each of the external connection pads in one face of the wiring board, an outer peripheral edge of the external connection pad is retracted from an outer peripheral edge of the surface plated layer toward a center of the external connection pad.

Other aspects and advantages of the invention will be apparent from the following description, the drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an external connection pad which is in the wiring board of the present invention, and in which the outer peripheral edge of the external connection pads is retracted from the outer peripheral edge of a surface plated layer toward the center of the external connection pad.

FIG. 2 is a view illustrating a crack which is formed between the surface plated layer and the insulating layer in the wiring board of the present invention.

FIGS. 3A to 3E are first views illustrating the production of a wiring board of Example 1.

FIGS. 4A to 4D are second views illustrating the production of the wiring board of Example 1.

FIG. 5 is a view showing a wiring board of Examples 1 and 2 on which a semiconductor chip is mounted.

FIG. 6 is a view showing the wiring board of Examples 1 and 2 in which a semiconductor chip is mounted on a face opposite to the case of the wiring board of FIG. 5.

FIGS. 7A to 7D are first views illustrating the production of the wiring board of Example 2.

FIGS. 8A to 8D are second views illustrating the production of the wiring board of Example 2.

FIGS. 9A to 9E are first views illustrating the production of a wiring board of Example 3.

FIGS. 10A to 10D are second views illustrating the production of the wiring board of Example 3.

FIG. 11 is a view showing a wiring board of Examples 3 and 5 on which a semiconductor chip is mounted.

FIG. 12 is a view showing the wiring board of Examples 3 and 5 in which a semiconductor chip is mounted on a face opposite to the case of the wiring board of FIG. 11.

FIGS. 13A to 13F are first views illustrating the production of a wiring board of Example 4.

FIGS. 14A to 14D are second views illustrating a production of the wiring board of Example 4.

FIG. 15 is a view showing the wiring board of Example 4 on which a semiconductor chip is mounted.

FIG. 16 is a view showing the wiring board of Example 4 in which a semiconductor chip is mounted on a face opposite to the case of the wiring board of FIG. 15.

FIGS. 17A to 17F are first views illustrating a production of the wiring board of Example 5.

FIGS. 18A to 18D are second views illustrating a production of the wiring board of Example 5.

FIGS. 19A to 19F are first views illustrating a production of a wiring board of Example 6.

FIGS. 20A to 20D are second views illustrating a production of the wiring board of Example 6.

FIG. 21 is a view showing the wiring board of Example 6 on which a semiconductor chip is mounted.

FIG. 22 is a view showing the wiring board of Example 6 in which a semiconductor chip is mounted on a face opposite to the case of the wiring board of FIG. 21.

FIGS. 23A to 23F are first views illustrating a production of a wiring board of Example 7.

FIGS. 24A to 24D are second views illustrating a production of the wiring board of Example 7.

FIG. 25 is a view showing the wiring board of Example 7 on which a semiconductor chip is mounted.

FIG. 26 is a view showing the wiring board of Example 7 in which a semiconductor chip is mounted on a face opposite to the case of the wiring board of FIG. 25.

FIG. 27 is a view illustrating an external connection pad in a related-art wiring board which is produced by a build-up technique.

FIG. 28 is a view illustrating an external connection pad in another related-art wiring board.

FIG. 29 is a view illustrating a crack which is formed between a surface plated layer and an insulating layer in a pad portion shown in FIG. 28.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A wiring board of the present invention is characterized in that an outer peripheral edge of each of external connection pads in one face is retracted from an outer peripheral edge of a surface plated layer toward the center of the external connection pad.

FIG. 1 shows an external connection pad 1. The pad 1 has a surface plated layer 2 on the side of connection to an external circuit. As an example, each of the pad 1 and the surface plated layer 2 is formed in a circular shape from a planar view. A center of the surface plated layer 2 coincides with a center of the pad 1. In the pad 1, an outer peripheral edge 1 a is retracted from an outer peripheral edge 2 a of the surface plated layer 2 toward the center of the pad 1, and positioned inside the outer peripheral edge 2 a of the surface plated layer 2. In order to attain the object of the present invention, preferably, the pad 1 is made as small as possible. However, the lower limit of the size depends mainly on the production accuracy which is required for ensuring joining of the pad 1 and a via 3 for connecting the pad 1 to a wiring 4 in the board. By contrast, the size of the surface plated layer 2 which is joined to the pad 1 depends on that of a bump (not shown) which is to be connected. The actual size of the pad 1 should be determined in view of these dependencies. In a standard wiring board, for example, the horizontal distance (the length indicated by D in FIG. 1) between the outer peripheral edge 1 a of the pad 1 and the outer peripheral edge 2 a of the surface plated layer 2 may be set to be about 0.1 to 5 μm, preferably, about 1 to 3 μm.

Referring to FIG. 1, the via 3 is connected to the wiring 4 through a pad 5 which is at a position corresponding to the external connection pad 1, and which is positioned in one end of the wiring 4. The external connection pad 1, the surface plated layer 2, the via 3, the wiring 4, and the pad 5 connected to the wiring 4 are in an insulating layer 7 except the upper face of the surface plated layer 2.

In the related art which has been described with reference to FIG. 27, the size of the opening portion 107 of the solder resist layer 106 which is connected to the pad 101 for connecting with an external circuit defines that of the surface plated layer 108 which is positioned there, and depends on that of a bump to be connected. Because, after the solder resist layer 106 which covers the pad 101 is formed, the opening portion 107 must be formed in the solder resist layer 101, the pad 101 must be formed to be larger than the opening portion 107 or larger than the surface plated layer 108. In this case, the outer peripheral edge of the pad 101 is inevitably positioned outside that of the surface plated layer 108.

In the present invention, by contrast, the outer peripheral edge 1 a of the external connection pad 1 is retracted from the outer peripheral edge 2 a of the surface plated layer 2 toward the center of the pad, and the former is positioned inside the latter (FIG. 1). The retraction of the outer peripheral edge 1 a of the external connection pad 1 toward the center of the pad enables the wirings of the wiring board of the present invention to be miniaturized, and reduces the amount of a resin which is between the external connection pad 1 and the pad 5 connected to the inner wiring 4, i.e., a resin which is surrounded by vertical broken lines B shown in FIG. 1, the lower face of the pad 1, the upper face of the pad 5, and the side face of the via 3, as compared with the case of the related art which has been described with reference to FIG. 27. Therefore, it is possible to maintain the connection reliability of the via against stress caused by heat shrinkage of the resin.

In the related art which has been described with reference to FIG. 28, the crack 131 which is formed due to stress between the surface plated layer 122 and the insulating layer 123 easily propagates toward the interior of the insulating layer 123 along the side face of the pad 121 as shown in FIG. 29, and therefore there is a problem in that the propagation easily causes the performance of the wiring board to be degraded.

In the present invention, by contrast, a crack 9 which is formed between the surface plated layer 2 and the insulating layer 7 propagates along the side face of the surface plated layer 2 and stops there as shown in FIG. 2, so that the crack does not penetrate very deeply into the insulating layer 7. Therefore, the problem in that the performance of the wiring board is degraded is avoided.

In the present invention, the term “external circuit” means a circuit which is outside the wiring board, and to which the wiring board is to be connected. For example, “external circuit” in the present invention is a circuit of a semiconductor chip or another electronic component which is to be mounted on the wiring board, that of a mounting board to which a wiring board on which such a semiconductor chip and the like are mounted is to be connected, or the like.

The materials of the members constituting the wiring board of the present invention may be similar to those of equivalent members in a usual wiring board. As the material of the external connection pad, for example, a usual wiring material such as copper (Cu) or a copper alloy may be used. As the material of the surface plated layer disposed on the external connection pad, (1) a combination of Ni and Au, (2) a combination of Ni, Pd, and Au, (3) Sn, (4) a combination of Sn and Ag, or the like may be used. In the case of the combination of (1), (2), or (4), plated layers are sequentially stacked so that the Au layer or the Ag layer is exposed to the outside.

The wiring board of the present invention can be produced by a method in which external connection pads are first formed together with surface plated layers on a support member made of a metal such as a copper plate or a copper foil, required numbers of insulating layers and wiring layers are formed on the external connection pads by a build-up technique, external connection pads are formed on the opposite side are formed, and thereafter the support member is removed. A process of retracting the outer peripheral edge of each of the external connection pads of one face of the wiring board from that of the surface plated layer toward the center of the pad can be performed before the initial formation of the surface plated layer by a build-up technique.

In the thus produced wiring board of the present invention, the external connection pads which are initially formed on the support member are pads in each of which the outer peripheral edge is retracted from that of the surface plated layer toward the center of the pad, and by contrast the external connection pads on the opposite side (the final pads formed by the build-up technique) are larger than the surface plated layer. Mainly, the former pads are used for mounting a semiconductor chip or another electronic component on the wiring board, and the latter pads are used for mounting the wiring board on a mounting board. In some cases, nevertheless, the pads may be used in the opposite manner.

EXAMPLES

Next, the present invention will be further described by way of examples. However, the present invention is not restricted to the examples described below.

Example 1

In Example 1, a wiring board in which the surface of a surface plated layer and that of a wiring board are in the same plane will be described together with a method producing it.

As shown in FIG. 3A, a plate resist pattern 12 which will be used as a mask pattern is formed on the surface of a Cu plate serving as a support member 11. In FIG. 3A, for the sake of simplicity, only the resist pattern 12 on one face of the support member 11 is shown. Actually, also the opposite face of the support member 11 is covered by a plate resist pattern. As the support member 11, other than a Cu plate, a Cu foil or a plate or foil of another metal or alloy which can be removed by a usual etchant may be used. As shown in FIG. 3B, surface plated layers 13 and external connection pads 14 are sequentially formed by electrolytic plating on the support member 11 which is exposed in bottom portions of opening portions 12 a (FIG. 3A) (having a diameter of 100 μm) of the plate resist pattern 12. The electrolytic plating is performed by feeding power from the support member 11. Here, each thickness of the external connection pads 14 is greater than each thickness of the surface plated layers 13. Each of the surface plated layers 13 is formed by an Au layer and Ni layer respectively having thicknesses of 0.5 μm and 5 μm (the Au layer and the Ni layer are formed in this sequence). The external connection pads 14 are formed by Cu so as to have a thickness of 10 μm.

Next, while using an etchant which dissolves only Cu, the external connection pads 14 are selectively etched so that the outer peripheral edges of the external connection pads 14 are made smaller by about 1 to 3 μm than the outer peripheral edges of the surface plated layers 13 (FIG. 3C). After etching, the plate resist pattern 12 is removed (FIG. 3D), and then a resin film is laminated over the whole face so as to cover the pads 14, thereby forming an insulating layer 15 (FIG. 3E). As the resin film, a film of epoxy, polyimide, or the like may be used.

As shown in FIG. 4A, next, via holes 15 a are formed in the insulating layer 15 by laser processing. The diameter of each of the via holes 15 a is 60 μm in the surface of the insulating layer 15, and about 50 μm in the bottom portion from which the pad 14 is exposed, so that the via hole 15 a is formed into a circular truncated cone-like shape in which the opening portion side has a larger diameter. Then, vias 16 a connected to the pads 14, and a wiring pattern for a wiring layer 16 b connected to the vias 16 a are formed (FIG. 4B). For example, the wiring layer 16 b is formed by copper. In this process, for example, a usual method such as the semi-additive method can be used.

The formation of an insulating layer, and that of vias and a wiring layer are repeated to form predetermined numbers of insulating layers 15 and wiring layers 16 b as shown in FIG. 4C, and the external connection pads 17 (having a diameter of 200 to 1,000 μm) are formed together with a wiring pattern on the uppermost insulating layer 15. Then, a solder resist layer 18 having opening portions 18 a which are connected to the pads 17 is formed. Furthermore, surface plated layers 19 are formed by electroless plating on the pads 17 which are exposed in the opening portions 18 a. In the surface plated layers 19, for example, a Ni layer and an Au later are formed in this order. Other words, the surface plated layers 19 are formed of the Ni layer and the Au layer so as to expose the Au layer externally. Thereafter, the support member 11 is removed by etching, thereby completing a wiring board 10 as shown in FIG. 4D. In the completed wiring board 10, the pads 14 in the face 10 a from which the support member 11 is removed are used as pads for connecting with a semiconductor chip or the like, and the pads 17 in the opposite face are used as pads for connecting with a mounting board.

FIG. 5 shows the wiring board 10 on which a semiconductor chip 21 is mounted. The semiconductor chip 21 is connected to the pads 14 of the wiring board 10 by solder joining members 22 which are formed by reflowing bumps that are previously disposed on the semiconductor chip 21. The gap between the wiring board 10 and the semiconductor chip 21 is filled with an underfill resin 23.

As shown in FIG. 6, the semiconductor chip 21 may be connected to the pads 17 in the face opposite to the face 10 a of the wiring board 10 from which the support member 11 is removed. In this case, the pads 14 in the face 10 a of the wiring board 10 from which the support member 11 is removed are used as pads for connecting a mounting board (not shown).

Example 2

Hereinafter, a wiring board in which the surface of a surface plated layer and that of a wiring board are in the same plane will be described together with another method producing it.

As shown in FIG. 7A, a plate resist pattern 32 is formed on the surface of a Cu plate serving as a support member 31 (a resist layer (not shown) is formed also on the rear face of the support member 31). As the support member 31, other than a Cu plate, a Cu foil or a plate or foil of another metal or alloy which can be removed by a usual etchant may be used. As shown in FIG. 7B, surface plated layers 33 and external connection pads 34 are sequentially formed by electrolytic plating on the support member 31 which is exposed in bottom portions of opening portions 32 a (FIG. 7A) (having a diameter of 100 μm) of the plate resist pattern 32. As each of the surface plated layers 33, an Au layer and Ni layer respectively having thicknesses of 0.5 μm and 5 μm are formed in this sequence. The external connection pads 34 are formed by Ni so as to have a thickness of 10 μm.

Next, the plate resist pattern 32 is peeled off, and then the external connection pads 34 made of Ni are selectively etched so that the outer peripheral edges of the external connection pads 34 are made smaller by about 1 to 3 μm than the outer peripheral edges of the plated layers 33 (FIG. 7C). As shown in FIG. 7D, thereafter, a resin film is laminated over the whole face so as to cover the external connection pads 34, thereby forming an insulating layer 35. In the formation of the insulating layer 35, a resin film of epoxy, polyimide, or the like may be used.

As shown in FIG. 8A, next, via holes 35 a are formed in the insulating layer 35 by laser processing. The diameter of each of the via holes 35 a is 60 μm in the surface of the insulating layer 35, and about 50 μm in the bottom portion from which the pad 34 is exposed. Then, vias 36 a connected to the pads 34, and a wiring layer 36 b connected to the vias are formed by, for example, the semi-additive method (FIG. 8B).

Then, the formation of an insulating layer, and that of vias and a wiring layer are repeated to form predetermined numbers of insulating layers 35 and wiring layers 36 b as shown in FIG. 8C, and external connection pads 37 (having a diameter of 200 to 1,000 μm) are formed together with a wiring pattern on the uppermost insulating layer 35. Then, a solder resist layer 38 having opening portions 38 a which are connected to the pads 37 is formed. Furthermore, surface plated layers 39 are formed by electroless plating on the pads 37 which are exposed in the opening portions 38 a. Thereafter, the support member 31 is removed by etching, thereby completing a wiring board 30 as shown in FIG. 8D. In the completed wiring board 30, the pads 34 in the face 30 a from which the support member 31 is removed are used as pads for connecting with a semiconductor chip or the like, and the pads 37 in the opposite face are used as pads for connecting with a mounting board. In this case, the configuration where a semiconductor chip is connected to the wiring board 30 is identical with that in the case of the wiring board 10 of Example 1, or as exemplarily shown in FIG. 5.

Similarly with the case of the wiring board 10 of Example 1, also in the wiring board 30 of Example 2, the semiconductor chip may be connected to the pad 37 in the face of the wiring board 30 opposite to the face 30 a from which the support member 31 is removed. In this case, as shown in FIG. 6, the pads 34 in the face 30 a of the wiring board 30 from which the support member 31 is removed are used as pads for connecting a mounting board (not shown).

Example 3

Hereinafter, an example of a wiring board in which a surface plated layer is positioned in a recess of the wiring board will be described together with a method producing it. The materials and dimensions of the members, the processing methods, and the like used in the following examples are identical with those described in Examples 1 and 2, unless otherwise specified.

As shown in FIG. 9A, a plate resist pattern 42 having opening portions 42 a is formed on the surface of a Cu plate serving as a support member 41 (a resist layer (not shown) is formed also on the rear face of the support member 41). As shown in FIG. 9B, surface plated layers 43 (formed by an Au layer and a Ni layer) and external connection pads 44 made of Cu are sequentially formed by electrolytic plating on the support member 41 which is exposed in bottom portions of opening portions 42 a.

After the plate resist pattern 42 is removed (FIG. 9C), the Cu material is selectively etched so that, as shown in FIG. 9D, the outer peripheral edges of the pads 44 are made smaller by about 1 to 3 μm than the outer peripheral edges of the surface plated layers 43, and a part of the support member 41 made of the Cu material is dissolved away by side etching and undercut due to the mask effect of the surface plated layers 43, so that peripheral edge portions of the surface plated layers 43 on the side contacted with the support member 41 are exposed. Therefore, projections 41 a having a height of about 1 to 3 μm are formed on the support member 41, and the surface plated layers 43 and the pads 44 are placed on the projections 41 a. After the etching, a resin film is laminated over the whole face so as to cover the pads 44, thereby forming an insulating layer 45 (FIG. 9E).

As shown in FIG. 10A, next, via holes 45 a are formed in the insulating layer 45 by laser processing. As shown in FIG. 10B, thereafter, vias 46 a connected to the pads 44, and a wiring pattern for a wiring layer 46 b connected to the vias 46 a are formed.

The formation of an insulating layer, and that of vias and a wiring layer are repeated to form predetermined numbers of insulating layers 45 and wiring layers 46 b as shown in FIG. 10C, external connection pads 47 are formed together with a wiring pattern on the uppermost insulating layer 45, and thereafter a solder resist layer 48 having opening portions 48 a which are connected to the pads 47 is formed. Next, surface plated layers 49 are formed by electroless plating on the pads 47 which are exposed in the opening portions 48 a. Thereafter, the support member 41 is removed together with the projections 41 a by etching, thereby completing a wiring board 40 as shown in FIG. 10D. In the completed wiring board 40, the pads 44 in the face 40 a from which the support member 41 is removed are used as pads for connecting with a semiconductor chip or the like, and the pads 47 in the opposite face are used as pads for connecting with a mounting board.

In the wiring board 40 of Example 3, by the removal of the support member 41 by etching, recesses 45 b in which the opening portions on the side of the face 40 a have a larger diameter in conforming to the shape of the projections 41 a of the support member 41 are formed in the insulating layer 45 which has been contacted with the support member 41. Because of the recesses 45 b, in the case where a semiconductor chip is flip chip connected to the wiring board 40, when bumps of the semiconductor chip are positioned in the recesses 45 b, the bumps can be easily connected to the wiring board, and the positioning of the chip can be facilitated. Moreover, the peripheral edge portions of the surface plated layers 43 are covered by the insulating layer 45, and hence the adhesion strength of the surface plated layers 43 to the wiring board 40 is improved.

FIG. 11 shows the wiring board 40 on which the semiconductor chip 21 is mounted. The semiconductor chip 21 is connected to the pads 44 positioned in the recesses 45 b (FIG. 10D) of the wiring board 40, by the solder joining members 22 which are formed by reflowing bumps that are previously disposed on the semiconductor chip 21. The gap between the wiring board 40 and the semiconductor chip 21 is filled with the underfill resin 23.

As shown in FIG. 12, the semiconductor chip 21 may be connected to the pads 47 in the face opposite to the face 40 a of the wiring board 40 from which the support member 41 is removed. In this case, the pads 44 in the face 40 a of the wiring board 40 from which the support member 41 is removed are used as pads for connecting a mounting board (not shown).

Example 4

Hereinafter, another example of a wiring board in which a surface plated layer is positioned in a recess of the wiring board will be described together with a method producing it.

As shown in FIG. 13A, a plate resist pattern 52 having opening portions 52 a is formed on the surface of a Cu plate serving as a support member 51 (a resist layer (not shown) is formed also on the rear face of the support member 51). Sacrificial layers 51′ (having a thickness of 1 to 30 μm) which are made of Cu of the same material as the support member 51 are formed by electrolytic plating on the support member 51 which is exposed in bottom portions of opening portions 52 a (FIG. 13B). When the support member 51 is removed later, also the sacrificial layers 51′ are removed together with the support member 51. Therefore, the sacrificial layers 51′ are preferably made of the same material as the support member 51. As shown in FIG. 13C, thereafter, surface plated layers 53 (formed by an Au layer and a Ni layer) and external connection pads 54 made of Cu are formed similarly by electrolytic plating in a sequential manner.

Next, the outer peripheral edges of the pads 54 are made smaller by about 1 to 3 μm than the outer peripheral edges of the surface plated layers 53 as shown in FIG. 13D, by selective etching of Cu, and then the plate resist pattern 52 is removed (FIG. 13E). Thereafter, a resin film is laminated over the whole face so as to cover the pads 54, thereby forming an insulating layer 55 (FIG. 13F).

As shown in FIG. 14A, next, via holes 55 a are formed in the insulating layer 55 by laser processing. As shown in FIG. 14B, thereafter, vias 56 a connected to the pads 54, and a wiring pattern for a wiring layer 56 b connected to the vias 56 a are formed.

The formation of an insulating layer, and that of vias and a wiring layer are repeated to form predetermined numbers of insulating layers 55 and wiring layers 56 b as shown in FIG. 14C, external connection pads 57 are formed together with a wiring pattern on the uppermost insulating layer 55, and thereafter a solder resist layer 58 having opening portions 58 a which are connected to the pads 57 is formed. Next, surface plated layers 59 are formed by electroless plating on the pads 57 which are exposed in the opening portions 58 a. Thereafter, the support member 51 is removed together with the sacrificial layers 51′ by etching, thereby completing a wiring board 50 as shown in FIG. 14D. In the completed wiring board 50, the pads 54 in the face 50 a from which the support member 51 is removed are used as pads for connecting with a semiconductor chip or the like, and the pads 57 in the opposite face are used as pads for connecting with a mounting board.

In the wiring board 50 of Example 4, by the removal of the support member 51 by etching, recesses 55 b in which the opening portions on the side of the face 50 a have a larger diameter in conforming to the shape of the sacrificial layers 51′ are formed in the insulating layer 55 which has been contacted with the support member 51. Because of the recesses 55 b, in the case where a semiconductor chip is flip chip connected to the wiring board, when bumps of the semiconductor chip are positioned in the recesses 55 b, the bumps can be easily connected to the wiring board, and the positioning of the chip can be facilitated.

FIG. 15 shows the wiring board 50 on which the semiconductor chip 21 is mounted. The semiconductor chip 21 is connected to the pads 54 positioned in the recesses 55 b (FIG. 14D) of the wiring board 50, by the solder joining members 22 which are formed by reflowing bumps that are previously disposed on the semiconductor chip 21. The gap between the wiring board 50 and the semiconductor chip 21 is filled with the underfill resin 23.

As shown in FIG. 16, the semiconductor chip 21 may be connected to the pads 57 in the face opposite to the face 50 a of the wiring board 50 from which the support member 51 is removed. In this case, the pads 54 in the face 50 a of the wiring board 50 from which the support member 51 is removed are used as pads for connecting a mounting board (not shown).

Example 5

Hereinafter, a further example of a wiring board in which a surface plated layer is positioned in a recess of the wiring board will be described together with a method producing it.

As shown in FIG. 17A, a plate resist pattern 62 having opening portions 62 a is formed on the surface of a Cu plate serving as a support member 61 (a resist layer (not shown) is formed also on the rear face of the support member 61). Sacrificial layers 61′ (having a thickness of 1 to 30 μm) which are made of Cu of the same material as the support member 61 are formed by electrolytic plating on the support member 61 which is exposed in bottom portions of opening portions 62 a (FIG. 17B). As shown in FIG. 17C, thereafter, surface plated layers 63 (formed by an Au layer and a Ni layer) and external connection pads 64 made of Cu are formed similarly by electrolytic plating in a sequential manner.

After the plate resist pattern 62 is removed (FIG. 17D), the Cu material is selectively etched so that, as shown in FIG. 17E, the outer peripheral edges of the pads 64 are made smaller by about 1 to 3 μm than the outer peripheral edges of the surface plated layers 63, and a part of the support member 61 made of the Cu material, and a part of the sacrificial layers 61′ are dissolved away by side etching and undercut due to the mask effect of the surface plated layers 63, so that peripheral edge portions of the surface plated layers 63 on the side contacted with the support member 61 are exposed. Therefore, projections 61 a having a height of about 1 to 3 μm are formed on the support member 61, and the sacrificial layers 61′, the surface plated layers 63, and the pads 64 are placed on the projections 61 a. After the etching, a resin film is laminated over the whole face so as to cover the pads 64, thereby forming an insulating layer 65 (FIG. 17F).

As shown in FIG. 18A, next, via holes 65 a are formed in the insulating layer 65 by laser processing. As shown in FIG. 18B, thereafter, vias 66 a connected to the pads 64, and a wiring pattern for a wiring layer 66 b connected to the vias 66 a are formed.

The formation of an insulating layer, and that of vias and a wiring layer are repeated to form predetermined numbers of insulating layers 65 and wiring layers 66 b as shown in FIG. 18C, external connection pads 67 are formed together with a wiring pattern on the uppermost insulating layer 65, and thereafter a solder resist layer 68 having opening portions 68 a which are connected to the pads 67 is formed. Next, surface plated layers 69 are formed by electroless plating on the pads 67 which are exposed in the opening portions 68 a. Thereafter, the support member 61 is removed together with the projections 61 a and the sacrificial layers 61′ by etching, thereby completing a wiring board 60 as shown in FIG. 18D. In the completed wiring board 60, the pads 64 in the face 60 a from which the support member 61 is removed are used as pads for connecting with a semiconductor chip or the like, and the pads 67 in the opposite face are used as pads for connecting with a mounting board.

In the wiring board 60 of Example 5, by the removal of the support member 61 by etching, recesses 65 b which conform to the shapes of the projections 61 a of the support member 61 and the sacrificial layers 61′ are formed in the insulating layer 65 which has been contacted with the support member 61. Because of the recesses 65 b, in the case where a semiconductor chip is flip chip connected to the wiring board 60, when bumps of the semiconductor chip are positioned in the recesses 65 b, the bumps can be easily connected to the wiring board, and the positioning of the chip can be facilitated. Since also the sacrificial layers 61′ is removed in the formation of the recesses 65 b by etching, deeper recesses can be formed. Moreover, the peripheral edge portions of the surface plated layers 63 are covered by the insulating layer 65, and hence the adhesion strength of the surface plated layers 63 to the wiring board 60 is improved.

The configuration of Example 5 where a semiconductor chip is connected to the wiring board 60 is basically identical with that in the case of the wiring board 40 of Example 3, or as exemplarily shown in FIG. 11. Similarly with the case of the wiring board 40 of Example 3, also in the case of the wiring board 60 of Example 5, the semiconductor chip may be connected to the pads 67 in the face opposite to the face 60 a of the wiring board 60 from which the support member 61 is removed. In this case, as shown in FIG. 12, the pads 64 in the face 60 a of the wiring board 60 from which the support member 61 is removed are used as pads for connecting a mounting board (not shown).

Example 6

Hereinafter, an example of a wiring board in which a surface plated layer is projected from the surface of the wiring board will be described together with a method producing it.

As shown in FIG. 19A, a plate resist pattern 72 having opening portions 72 a is formed on the surface of a Cu plate serving as a support member 71 (a resist layer (not shown) is formed also on the rear face of the support member 71). The support member 71 is etched while using the resist pattern 72 as a mask, to form semispherical recesses 71 a in the support member 71 (FIG. 19B). As shown in FIG. 19C, then, surface plated layers 73 (formed by an Au layer and a Ni layer) and external connection pads 74 made of Cu are sequentially formed by electrolytic plating in the recesses 71 a.

Next, the outer peripheral edges of the pads 74 are made smaller by about 1 to 3 μm than the outer peripheral edges of the surface plated layers 73 as shown in FIG. 19D, by selective etching of Cu, and then the plate resist pattern 72 is removed (FIG. 19E). Thereafter, a resin film is laminated over the whole face so as to cover the pads 74, thereby forming an insulating layer 75 (FIG. 19F).

As shown in FIG. 20A, next, via holes 75 a are formed in the insulating layer 75 by laser processing. As shown in FIG. 20B, thereafter, vias 76 a connected to the pads 74, and a wiring pattern for a wiring layer 76 b connected to the vias 76 a are formed.

The formation of an insulating layer, and that of vias and a wiring layer are repeated to form predetermined numbers of insulating layers 75 and wiring layers 76 b as shown in FIG. 20C, external connection pads 77 are formed together with a wiring pattern on the uppermost insulating layer 75, and thereafter a solder resist layer 78 having opening portions 78 a which are connected to the pads 77 is formed. Next, surface plated layers 79 are formed by electroless plating on the pads 77 which are exposed in the opening portions 78 a. Thereafter, the support member 71 is removed by etching, thereby completing a wiring board 70 as shown in FIG. 20D. In the completed wiring board 70, the pads 74 in the face 70 a from which the support member 71 is removed are used as pads for connecting with a semiconductor chip or the like, and the pads 77 in the opposite face are used as pads for connecting with a mounting board.

FIG. 21 shows the wiring board 70 on which the semiconductor chip 21 is mounted. The semiconductor chip 21 is connected to the pads 74 of the wiring board 70, by the solder joining members 22 which are formed by reflowing bumps that are previously disposed on the semiconductor chip 21. Since the pads 74 are projected, the connection can be suitably performed even when the solder joining members 22 are fine and have a small diameter. The gap between the wiring board 70 and the semiconductor chip 21 is filled with the underfill resin 23.

As shown in FIG. 22, the semiconductor chip 21 may be connected to the pads 77 in the face opposite to the face 70 a of the wiring board 70 from which the support member 71 is removed. In this case, the pads 74 in the face 70 a of the wiring board 70 from which the support member 71 is removed are used as pads for connecting a mounting board (not shown).

Example 7

Hereinafter, another example of a wiring board in which a surface plated layer is projected from the surface of the wiring board will be described together with a method producing it.

As shown in FIG. 23A, a plate resist pattern 82 having opening portions 82 a is formed on the surface of a Cu plate serving as a support member 81 (a resist layer (not shown) is formed also on the rear face of the support member 81). The support member 81 is etched while using the resist pattern 82 as a mask, to form semispherical recesses 81 a in the support member 81 (FIG. 23B). As shown in FIG. 23C, then, surface plated layers 83 (formed by an Au layer and a Ni layer) and external connection pads 84 made of Cu are sequentially formed by electrolytic plating in the recesses 81 a.

After the plate resist pattern 82 is removed (FIG. 23D), the Cu material is selectively etched so that, as shown in FIG. 23E, the outer peripheral edges of the pads 84 are made smaller by about 1 to 3 μm, and a part of the support member 81 made of the Cu material is dissolved away by side etching and undercut by an etchant, so that peripheral edge portions of the surface plated layers 83 on the side contacted with the support member 81 are exposed. Thereafter, a resin film is laminated over the whole face so as to cover the pads 84, thereby forming an insulating layer 85 (FIG. 23F).

As shown in FIG. 24A, next, via holes 85 a are formed in the insulating layer 85 by laser processing. As shown in FIG. 24B, thereafter, vias 86 a connected to the pads 84, and a wiring pattern for a wiring layer 86 b connected to the vias 86 a are formed.

The formation of an insulating layer, and that of vias and a wiring layer are repeated to form predetermined numbers of insulating layers 85 and wiring layers 86 b as shown in FIG. 24C, external connection pads 87 are formed together with a wiring pattern on the uppermost insulating layer 85, and thereafter a solder resist layer 88 having opening portions 88 a which are connected to the pads 87 is formed. Next, surface plated layers 89 are formed by electroless plating on the pads 87 which are exposed in the opening portions 88 a. Thereafter, the support member 81 is removed by etching, thereby completing a wiring board 80 as shown in FIG. 24D. In the wiring board 80, the peripheral edge portions of the surface plated layers 83 are covered by the insulating layer 85, and hence the adhesion strength of the surface plated layers 83 to the wiring board 80 is improved. In the wiring board 80, moreover, the pads 84 in the face 80 a from which the support member 81 is removed are used as pads for connecting with a semiconductor chip or the like, and the pads 87 in the opposite face are used as pads for connecting with a mounting board.

FIG. 25 shows the wiring board 80 on which the semiconductor chip 21 is mounted. The semiconductor chip 21 is connected to the pads 84 of the wiring board 80, by the solder joining members 22 which are formed by reflowing bumps that are previously disposed on the semiconductor chip 21. The gap between the wiring board 80 and the semiconductor chip 21 is filled with the underfill resin 23.

As shown in FIG. 26, the semiconductor chip 21 may be connected to the pads 87 in the face opposite to the face 80 a of the wiring board 80 from which the support member 81 is removed. In this case, the pads 84 in the face 80 a of the wiring board 80 from which the support member 81 is removed are used as pads for connecting a mounting board (not shown).

While the present inventive concept has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims. 

1. A wiring board comprising: wiring layers; insulating layers disposed between said wiring layers; and external connection pads respectively including surface plated layers, wherein, in each of said external connection pads in one face of said wiring board, an outer peripheral edge of said external connection pad is retracted from an outer peripheral edge of said surface plated layer toward a center of said external connection pad, and peripheral edge portions of said surface plated layers in said one face are covered by one of said insulating layers of said wiring board.
 2. A wiring board according to claim 1, wherein said surface plated layers in said one face are positioned in recesses of a surface of said wiring board, respectively.
 3. A wiring board according to claim 1, wherein said surface plated layers in said one face are projected from a surface of said wiring board.
 4. A wiring board according to claim 1, wherein said external connection pads in said one face are pads for mounting a semiconductor chip or another electronic component on said wiring board.
 5. A wiring board according to claim 1, wherein said external connection pads in said one face are pads for mounting said wiring board on another board.
 6. A wiring board according to claim 1, wherein each of said surface plated layers includes a plurality of plated layers.
 7. A wiring board according to claim 1, wherein each of said external connection pads is made of at least one of copper and a copper alloy.
 8. A wiring board according to claim 1, wherein each of said external connection pads includes a semispherical surface, and each of said surface plated layers is provided on the semispherical surface.
 9. A wiring board according to claim 1, wherein a via of said wiring layers is connected to a face of each of said external connection pads opposite to a face on which each of said surface plated layers is formed.
 10. A wiring board according to claim 9, wherein via holes are formed in said insulating layers, said via holes for exposing the face of each of said external connection pads opposite to the face on which each of said surface plated layers is formed, wherein each of the via holes is formed into a circular truncated cone-like shape in which a portion of a surface side of the insulating layer has a larger diameter than a portion which exposes each of the external connection pads, and wherein said via is provided into each of the via holes.
 11. A wiring board comprising: wiring layers; insulating layers disposed between said wiring layers; and external connection pads respectively including surface plated layers, wherein, in each of said external connection pads in one face of said wiring board, an outer peripheral edge of said external connection pad is retracted from an outer peripheral edge of said surface plated layer toward a center of said external connection pad, and surfaces of said surface plated layers in said one face are positioned in a same plane as a surface of said wiring board, and an outer peripheral end surface of each of said surface plated layers directly abuts an inner end surface of the insulating layer which defines an opening in the insulating layers in which the surface plated layer is received such that said surface of said wiring board is a continuous planar surface formed of a face of the surface plated layers and a face of the insulating layers.
 12. A wiring board according to claim 11, wherein said external connection pads in said one face are pads for mounting a semiconductor chip or another electronic component on said wiring board.
 13. A wiring board according to claim 11, wherein said external connection pads in said one face are pads for mounting said wiring board on another board.
 14. A wiring board according to claim 11, wherein each of said surface plated layers includes a plurality of plated layers.
 15. A wiring board according to claim 11, wherein each of said external connection pads is made of at least one of copper and a copper alloy.
 16. A wiring board according to claim 11, wherein each of said external connection pads includes a semispherical surface, and each of said surface plated layers is provided on the semispherical surface.
 17. A wiring board according to claim 11, wherein a via of said wiring layers is connected to a face of each of said external connection pads opposite to a face on which each of said surface plated layers is formed.
 18. A wiring board according to claim 17, wherein via holes are formed in said insulating layers, said via holes for exposing the face of each of said external connection pads opposite to the face on which each of said surface plated layers is formed, wherein each of the via holes is formed into a circular truncated cone-like shape in which a portion of a surface side of the insulating layer has a larger diameter than a portion which exposes each of the external connection pads, and wherein said via is provided into each of the via holes. 